JP 2013-252301A (Reference 1) discloses a technique has been proposed for estimating a three-dimensional position of an eye (eyeball) of a face included in a captured image (still image or moving image). An estimated eyeball center position can be used, for example, for calculation of a sight line angle (sight line direction). Since the eyeball center position differs depending on the skeleton or contour of each subject, in order to estimate the eyeball center position with higher accuracy, the prior calibration was necessary and the processing was complicated. Here, an estimation device has been proposed which estimates the three-dimensional position of the eyeball center without performing calibration with high accuracy. The estimation device calculates three-dimensional sight line vectors oriented to the three-dimensional position of the pupil center from the preset statistical three-dimensional position of the eyeball center for each of the left and right eyes, based on the estimated three-dimensional position posture of the face and the detected two-dimensional position of the pupil center on a face image. In addition, based on the time series of the three-dimensional sight line vectors of each of the left and right eyes, for example, optimum values of the three-dimensional positions of the eyeball centers of each of the left and right eyes in a face model coordinate system are estimated such that the errors of the three-dimensional positions of visual targets, such as each of the left and right eyes, are minimized.
However, for example, in a situation where the sight line angle (sight line direction) is used, there is a low possibility that a subject who estimates the eyeball center position stays still for a long time, and there is a case where a face direction irregularly changes. Therefore, there is a case where detection of the two-dimensional position of the pupil center, the coordinate system of the three-dimensional face model, and the like becomes unstable. In such a case, when the position of the eyeball center is estimated as it is, an error occurring in the two-dimensional position of the pupil center or the coordinate system of the three-dimensional face model is reflected in the estimated three-dimensional position of the eyeball position as it is, and there is a problem that the accuracy deteriorates. As a result, there are cases where the sight line angle (sight line direction) cannot be calculated correctly. Therefore, it is meaningful that an eyeball information estimation device, an eyeball information estimation method, and an eyeball information estimation program capable of suppressing deterioration of estimation accuracy of the eyeball center position can be provided since high accuracy in various types of processing using the eyeball center position, for example, calculation of the sight line angle, is achieved.